U.S. and South Korean military commanders are expressing satisfaction with the results of a four-day military exercise designed as a warning to North Korea.

About 20 ships, 200 aircraft and 8,000 personnel took part in the maneuvers in the Sea of Japan, which ended Wednesday with bombing runs and computer-simulated anti-submarine drills.

In Seoul, an official with the Joint Chiefs of Staff told reporters his nation's military had built confidence that it can deter any act of aggression from North Korea based on its alliance with the United States.

A U.S. military newspaper quoted the commander of one of the vessels in the exercise, Captain Paul Hogue on the USS Curtis Wilbur, saying he was confident that North Korea was paying attention to the exercise and that the intended signal had been sent.

The exercise was organized in response to the sinking of a South Korean warship, the Cheonan, in March. An international investigation concluded that a North Korean submarine had torpedoed the ship, killing 46 seamen. Pyongyang denies the charges and has repeatedly asked to send its own team to examine the wreckage of the ship.

The United States and South Korea plan several more joint exercises before the end of the year. At least some of those are expected to take place in the Yellow Sea, where the Cheonan was sunk.

China has objected to any U.S. naval exercise in the Yellow Sea, where it has sensitive ports and shipping lanes.